A method based on the mass-average retention of a heat-labile food component after exposure to a thermal process has been developed for estimating the Arrhenius activation energy (Ea) and reference reaction rate constant (k121 degrees C) for that component. The method involves: (1) heating the pureed food in containers such as 202 x 314 cans (with the requirement that the food heat by conduction), (2) determining the average concentration of the component remaining after a given time/temperature treatment, and (3) estimating Ea and K121 degrees C based on an iterative computer-assisted method. This method was compared to the TDTa can method (heating the pureed product in 208 x 006 cans) and the results based on the new averaging technique are: Chlorophyll in pea puree, Ea equals 22.5 kcal/mole, k121 degrees C equals 0.0210 min minus 1; chlorophyll in spinach puree, Ea equals 22.9 kcal/mole, k121 degrees C equals 0.0285 min; thiamine in pea puree, Ea equals 25.2 kcal/mole, k 121 degrees C equals 0.0144 min minus 1; thiamine in pork puree, Ea equals 27-1 kcal/mole, k121 degrees C equals 0.0245 min minus 1; betanine in beet puree, Ea equals 11.1 kcal/mole, k121 degrees C equals 0.0445 min minus 1. These results all agree within experimental error to those obtained in the TDT can method. The method will be used to determine Ea and k121 degrees C for vitamin B6 and pantothenic acid, two critical nutrients for which these data do not exist. These parameters will then be used to optimize thermal processes for retention of these vitamins.